[GN] Use correct toolchain for x64 target on Android

BUILD.gn

Index: BUILD.gn
diff --git a/BUILD.gn b/BUILD.gn
index 0af482b2c9ea711566acda9b9c941836f82d7cca..ded76e06c069cccfc7762e777352f46ed215bebd 100644
--- a/BUILD.gn
+++ b/BUILD.gn
@@ -1397,6 +1397,7 @@ source_set("v8_libbase") {
     libs = [ "dl", "rt" ]
   } else if (is_android) {
     defines += [ "CAN_USE_VFP_INSTRUCTIONS" ]
+    libs = [ "dl", "log" ]

[jochen (gone - plz use gerrit), 2015/03/27 11:59:56]

log is only needed for the target toolchain, no?

I'm surprised you don't need "rt" for host?

[haltonhuo, 2015/03/30 02:15:09]

Adding rt will cause -lrt not found error. Actually, after try the GYP and GN
build, I found another difference is: GYP use clang++, which GN uses g++. I
think we should change mksnapshot to built with clang.

So I added target_cpu == "x64" to let snapshot_toolchain use clang++. But I met
macro error "error Target architecture x64 is only supported on x64 host".

Any hint?

[haltonhuo, 2015/03/30 07:35:15]

Uploaded patch set2 is more correct way to go. Please review.

 
     if (host_os == "mac") {
       if (current_toolchain == host_toolchain) {